Do I believe the sky above or I do believe the sky above

Question

I’m Brazilian and I have a doubt. Why in Enya’s song “Caribbean Blue” does she say:

So the world goes round and round
With all you ever knew
They say the sky high above
Is Caribbean blue

If every man says all he can,
If every man is true,
Do I believe the sky above
Is Caribbean blue

Is it right ?

“Do I” is for questions, isn’t it?

Answer 1

The words "do I" can be used to indicate a question, as "do I turn left or right at Yonge St?" but it can also indicate emphasis, as "do I love chocolate!"